7 pieces, 1 3/4" X 1 1/8" the largest piece, 3/4" X 1/2" the smallest and so pretty it could be set in a ring. All smooth. Smooth flat shells work as well as a flat rock to get the chi flowing along your spine. This is a technique my chiropractor taught me. Convo me if you would like to know how to do it. It is invigorating to the body and helps your back.